Self-cooling lance for oxygen blowing

ABSTRACT

An oxygen blowing lance has a narrow annular or ring-shaped channel formed between a pair of spaced tubes having a relatively small flow area. This accelerates the speed of flow enough to generate a cooling effect which eliminates the need for any extraneous cooling, such as water cooling. A speed of oxygen flow between 400 and 900 meters per second (at standard conditions of 760 mm Hg. and 0*C) limits the wall temperature of the lance at the nozzle outlet to about 500*C and prevents spalling and burning off. The hollow or ring-shaped oxygen channel makes the lance remarkably strong and rigid. The ring-shaped channel may be elliptical, triangular or rectangular as well as circular. A ring-shaped or circular annular cross-section having a thickness of from about 3 to 10 mm and preferably from 4 to 7 mm is particularly advantageous. The cooling effect of the oxygen in the annular or ring-shaped channel is enhanced by installing a helical coil in the annular channel. This increases the rate of flow and cooling effect of the oxygen and the spiral path of flow also provides cooling. The helical pitch of the coil may vary along the length of the lance to provide any desired control of speed of flow and resistance. The cooling effect of the oxygen may be further improved by adding small quantities of water into the oxygen stream.

United States Patent 1191 Pfeifer Apr. 9, 1974 SELF-COOLING LANCE FOR OXYGEN 1 BLOWING Primary Examiner-Gerald A. Dost [75] Inventor: Ferdinand Pfeifer, Krefeld, Attorney or "9" and Hutz Germany [73] Assignee: Messer Griesheim GmbH, [57] ABSTRACT Frankfurt/Main, Germany An oxygen blowing lance has a narrow annular or ring-shaped channel formed between a pair of spaced [22] Flled 1972 tubes having a relatively small flow area. This acceler- [21] Appl. No.2 241,598 ates the speed of flow enough to generate a cooling effect which eliminates the need for any extraneous l cooling, such as water cooling. A speed of oxygen flow [30] Fore'gn Apphcamn Priority Data between 400 and 900 meters per second (at standard Apr. 10, 1971 Germany 2117714 Conditions of 7 0 Hg. and 0 limits the wall a temperature of the lance at the nozzle outlet to about [52] [1.8. CI. 266/34 L,' 239/488 500 and prevents spaning and burning off. The

[51 Int. Cl. CZlC 7/00 low or ring shaped Oxygen channel makes the lance [58] Fleld 0f Search 239/1325, 483, 488; remarkably strong and rigid. The ring shaped channel 266/34 34 LM may be elliptical, triangular or rectangular as well as circular. A ring-shaped or circular annular cross- [56] References cued section having a thickness of from about 3 to l0 mm UNITED STATES PATENTS and preferably from 4 to 7 mm is'particularly advanta- 481,088 8/1892 Chaney et ill 239/488 g The cooling effect f the xygen in the annular 1,494,675 5/1924 Ehrhart 239/483 or ring-shaped channel is enhanced by installing a he- 3,076,607 2/1963 Cordier 239/488 heal COll 1n the annular channel. Th1s lncreases the 313131919 10/1965 calzfflarim 239/483 rate of flow and cooling effect of the oxygen and the spiral path of flow also provides cooling. The helical or urn...

3,645,520 2/1972 Acre... 266 34 L {E 535:ig lgigfg igfig ga s? gg zgg fi 3,321,139 5/1967 DeSaint M61116... 266/34L p Th ff f h p b f 3,706,549 12/1972 Knuppeletal. 266/35 P e C00 3? t i g may 3,397,878 8/1968' 116111165 et a] 266/41 {her Improved y adding Small quantifies Of Water mto 3,504,856 4/1970 Hinkeldey et al. 266/34 L the yg Stream- 3,608,88O 9/1971 Gombert 266/41 3,703,279 11 1972 Saccamano et al 266/41 10 Claims, 2 Drawing Figures SHEET 2 BF 2 PATENTEUAPR 9 I974 Dem QmN sou can N l- I ooh 8m m 68- .I m mm 8: m 8m R 8 82 m 5 m 8& 9 3 82 Sh m 8 89 W 1 a M 89 W m 0 88 l rt m BACKGROUND OF THE INVENTION This invention relates to a self-cooling lance for oxygen blowing. Presently used oxygen blowinglances are either consumable or permanent. Consumable lances are immersed in the molten bath and advanced into it as the blowing proceeds until they are too short for usefuloperation. Their short lance life is tolerated in order to inject oxygen under the surface of the molten metal. Attempts have been made to lenghthen the service life of immersed lances by suitable selection of materials and protective coatings. Theextremely drastic thermal attack on the lance when it is immersed however prevents these measures from effectively lenghthening the life of such lances. This leaves remaining the cooling capacity of the oxygen blowing through the lance, which is not very successful in protecting it, and any other special cooling. methods are disregarded or avoided. i

Permanent oxygen blowing lances are used for refining molten steel by blowing oxygen into it. For these lances the relatively lower heat conditions permits various measures taken to preserve and protect the lance to result in an appreciable increase in service life. Ex-

tensive protective measures are therefore applied to permanent lances including the use of heat resistant, refractory, ceramic or flame-proof materials. Permanent lances are also provided with cooling conduits including single or multiple cooling canals, special coolants and oxygen conduits. All of these protective steps, particularly water cooling, are very complicated and expensive. They require circulating systems, pumps and in some instances heat exchangers forthe coolant and the like. An object of this invention is to provide a simple and economical method to prevent the rapid consumptionof oxygen blowing lances. Another object is to provide a self-cooling lance having a simple and economical structure.

7 SUMMARY OF THE INVENTION In accordance with this invention oxygen is conducted through a channel havinga ring-shaped crosssection adjoining the outer surface of the lance.

This novel process and corresponding lance structure cools the lance enough to eliminate the need for any extraneous cooling; such as water cooling. The channel is narrow enough to accelerate the speed of oxygen flow, for example, between 400 and 900 meters per second (at standard conditions of 760 mm Hg. and C). This unexpectedly limits the wall temperature of the lance at the nozzle outlet to about 500C. At this temperature neither spalling nor burning. off of the lance occurs. If oxygen were conducted at the afore' mentioned flow rate through a channel having a circular cross-section, its diameter would be so small that a lance of effective length, which must extend in most instances about 2 or 3 meters into the furnace, would not be strong enough to be structurally rigid. The hollow or ring-shaped oxygen channel of this invention is however remarkably strong and rigid. The ring-shaped channel may be elliptical, triangular or rectangular as well as circular. A ring-shaped or circular annular cross-section having a width of from about 3 to mm and preferably from 4 to 7 mm is particularly advantageous. The cooling effect of the oxygen in the annular or ring-shaped channel may be enhanced by installing a helical coil in the annular channel to divide it into a pair of parallel spiral or helically shaped conduits. This increases the rate of flow and cooling effect of the oxygen and the spiral path of flow also provides additional cooling. The helical pitch of the coil may vary along the length of the lance to provide any desired control of speed of flow and resistance. The cooling effect of the oxygen may be further improved by adding small quan tities of water into the oxygen stream.

BRIEF DESCRIPTION OF THE DRAWINGS Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

FIG. 1 is a cross-sectional view in elevation, broken in length, of an oxygen blowing lance which is one embodiment of this invention; and

. FIG. 2 is a graph of various operating characteristics of the lance shown in FIG. 1.

In FIG. 1, is shown a self-cooling oxygen blowing lance 10 including an elongated inner tube 1 within outer tube 2 which forms between them a narrow ringshaped annular slot 4 about 5 mm wide for conducting a flow of oxygen. Helical coil 3 having an angular pitch of 25.4 is installed in slot 4. Outer tube 2 is made of a heat resistant material, such as a refractoryor ceramic material or a specially heat-resistant steel, to protect it from penetration by the agitated molten metal.

The blowing oxygen is introduced into the lance through upper inlet connection 5 and about curved plug 12 at the top of inner tube 1 into annular slot 4 in the direction of the illustrated arrows. Spiral or helical coil 3 further increases the speed of the flow of oxygen and channels it in a spiral path. This increase in speed and spiral flow provide cooling effects which limit the temperature of the lance to about 500C and therefore effectively protect it against burning, spalling and scaling. The following computation illustrates the conditions obtained by a lance operated and made in accordance with this invention and it corresponds to the conditions shown on the graphic illustration provided in FIG. 2.

FIG. 2 shows conditions for a lance 10, having a length, L=2 m., operating in a 30-ton electric furnace having a wall radiating temperature of l,300C and a heat transfer factor of aStr 240 kcal/m hC. The oxygen throughput was taken on the basis of volume, V= L000 Nm' /h. N means at standard conditions. The slot width of the narrow annular slot is 5 mm with an outer tube 2 having an inside diameter of mm. The prede- At= Q/V C,,= 388C Cp is specific heat at constant pressure. b. Final Oxygen Temperature L 3309C..- 3. Annular slot measurements F V/C 1,000/3,600 515 0.54 l C is 0 speed 4. Angle of pitch of the coil sin a lO8/7r'80 0.43 25.4 5. Pressure loss P A p L 2.7 4.65 12.6 atmospheres absolute pressure. 6. Composition a. lance length: L 2 m b. 0 throughput: V 1,000 Nm /h Slot outer diameter: D,, 80 mm d) Slot inside diameter: D,- 70 mm d) Slot width: s 5 mm Average wall temperature: t,,, 350 C g. Angle of pitch of the spiral coil: or 25.4

h. Pressure lossz P 12.5 atmospheres absolute pressure i. Wall temperature at the nozzle outlet: t 500C Note: 45 here means approximately.

I claim:

1. A process for protecting a gaseous fluid blowing lance particularly a blowing lance for an industrial metal melting furnace characterized in that the gaseous blowingfluid is conducted through a ring-shaped zone in the lance contiguous with the outer surface of the lance, the zone being relatively thin on the order of from about 3 to mm., the distance across the ringshaped zone being substantially greater than the cross section of the zone, and the gaseous blowing fluid being provided to the zone under sufficient pressure to cause a flow of gaseous blowing fluid through the zone from about 400 to 900 meters per second at standard condidistance from the outer tube to provide a ring-shaped channel between them, an inlet connection on the lance, flow channeling means adjacent the inlet connection of the lance for conducting a flow of oxygen through the ring-shaped channel, the ring-shaped channel having a width of from about 3 to 10 mm whereby the flow'of oxygen is increased to a rate from about 400 to 900 meters. per second at standard conditions which is high enough to effectively cool the lance.

4. An oxygen blowing lance as set forth in claim 3 wherein the width of the ring-shaped channel is from about 4 to 7 mm.

5. A lance as set forth in claim 3 wherein the flow channeling means'includes a plug in the end of the inner tube disposed adjacent the inlet connection.

6. A lance as set forth in claim 3 wherein a spiral element is disposed in the ring-shaped channel to cause the oxygen flowing through it to flow in a spiral path whereby its cooling effect is enhanced.

7. A lance as set forth in claim 6 wherein the spiral element has a varying pitch whereby the cooling effect of the oxygen flow along the length of the lance is controlled.

8. A lance as set forth in claim 3 wherein the outer tube is a heat resistant material.

9. A lance as set forth in claim 8 wherein the outer tube is a refractory material.

10. A lance as set forth in claim 9 wherein the oute tube is a ceramic material. 

1. A process for protecting a gaseous fluid blowing lance particularly a blowing lance for an industrial metal melting furnace characterized in that the gaseous blowing fluid is conducted through a ring-shaped zone in the lance contiguous with the outer surface of the lance, the zone being relatively thin on the order of from about 3 to 10 mm., the distance across the ring-shaped zone being substantially greater than the cross section of the zone, and the gaseous blowing fluid being provided to the zone under sufficient pressure to cause a flow of gaseous blowing fluid through the zone from about 400 to 900 meters per second at standard conditions sufficient to cool the wall of the lance at its outlet to prevent spalling and burning.
 2. A process as set forth in claim 1 wherein the flow of gaseous blowing fluid is channeled in a helical path through the ring-shaped zone.
 3. An oxygen blowing lance comprising an outer tube, an inner tube disposed within and spaced a short distance from the outer tube to provide a ring-shaped channel between them, an inlet connection on the lance, flow channeling means adjacent the inlet connection of the lance for conducting a flow of oxygen through the ring-shaped channel, the ring-shaped channel having a width of from about 3 to 10 mm whereby the flow of oxygen is increased to a rate from about 400 to 900 meters per second at standard conditions which is high enough to effectively cool the lance.
 4. An oxygen blowing lance as set forth in claim 3 wherein the width of the ring-shaped channel is from about 4 to 7 mm.
 5. A lance as set forth in claim 3 wherein the flow channeling means includes a plug in the end of the inner tube disposed adjacent the inlet connection.
 6. A lance as set forth in claim 3 wherein a spiral element is disposed in the ring-shaped channel to cause the oxygen flowing through it to flow in a spiral path whereby its cooling effect is enhanced.
 7. A lance as set forth in claim 6 wherein the spiral element has a varying pitch whereby the cooling effect of the oxygen flow along the length of the lance is controlled.
 8. A lance as set forth in claim 3 wherein the outer tube is a heat resistant material.
 9. A lance as set forth in claim 8 wherein the outer tube is a refractory material.
 10. A lance as set forth in claim 9 wherein the outer tube is a ceramic material. 